Headstock flex

[Tiger]

Dear all,

I had been finding on the ol' Hare and Forbes 900 b/w centres that the headstock lifts slightly when I mount wood and engage the tailstock.The tighter that I did up the tailstock the more the headstock would lift. (BTW , I did the front lever that tightens the headstock up very tight).
I didn't notice any real major problems with spindle turning although it did make it harder for the headstock and tailstock to line up. What I did notice though was that when I was boring holes in wood that the holes were off-centre as there was noticeable lift from the headstock. Spoke to someone who suggested there was a nut that had come loose under the headstock (like the nut in the tailstock or banjo). I examined the headstock, there is no nut. What it has is a long thread with 2 clawed objects that grip the bed. They are sort of held in by a pin with a slot in it. On my lathe the front claw had this pin(?) the rear one did'nt. From what I could tell, the pin wasn't doing much except provide some sort of alignment for the claw. I used a nail at the rear end for the rear claw to align to thinking that this would help tighten down the headstock, it wasn't a lot better:mad: . For others that have had this problem, what did you do? I noticed the headstock is about a mm off the bed, I suppose that's so that it can swivel easier, but is that normal? Anyone who has one of these swivel head lathes will probably understand the set-up, what should I do?

[Grizz]

Hi Tiger. It does help if you put the proper pin in the back hole. I had the same problem and fixed most of it by doing this. There was a thread in here about it some time ago but I can't remember where it is now. Also, if it's the lathe that I'm thinking of (you know, it comes in all different colours, but, at the end of the day, they are all the same), I've had ongoing problems with the headstock shifting under load. They also need a more powerful motor on them.

Grizz.

[hughie]

Tiger, dont know if this helps but have a look at the link below. I had similar probs but on a MC1100.

http://www.woodworkforums.ubeaut.com.au/showthread.php?t=31145

hughie

[Tiger]

Grizz,

Do you know what that pin is called, what exactly does it do?

[Grizz]

Sorry Tiger, for the life of me, I can't remember what they are called. If you take the tensioning handle off, you can see the front one and measure it's diameter. It's a little bit tricky getting the back one in, but I think you'll find that it will help a lot.

Grizz.

[Tornatus]

G'day Tiger

The pin you are asking about is apparently called a "roll pin". See this thread for a discussion of your problem:

http://www.woodworkforums.ubeaut.com.au/showthread.php?t=15053&highlight=mc900

I had the same problem, caused by the tapered pin working loose. I fixed it by drilling the hole for the pin right through the locking bar, then fitting a high-tensile bolt & nyloc nut in place of the tapered pin. After tightening the whole assembly, I have not had a repeat of the headstock lifting.

[TTIT]

Tiger - the 'missing' pin is irrelevant - I had the same problem with my MC900 as does everyone else I think. The real problem is that the claw castings are badly done and dont seat properly at both ends so that as you are tightening the bolt, you are just bending it without pulling the claws down fully. If you look closely, you will find that the claw casting binds on the bolt before both ends of the claw even touch the headstock and bed. Hold the claw in place and see if you can slide the bolt right through to test for this problem. If you can't get the bolt through, touch the too-long end of the claw up with a file until the bolt slides through easily.
When I fixed mine, the first thing I noticed was that it would tighten in half a turn of the nut instead of the previous 10 turns which were just bending the bolt - big improvement.

[Tiger]

Thanks, guys, you've explained the problem, now I'll have a closer look at the assembley but my first thought was how crappy the castings of the claw component were.

[Skew ChiDAMN!!]

I agree with TTIT on this. One of the first things I do when "tuning" an untouched MC-X00 is strip the headstock down and do a smallscale clean-up with a file. Don't go overboard... you don't want to need to resort to shims. DAMHIKT. :o

As a bonus, I've found it usually also makes the whole process of rotating the head easier.

[Hickory]

I may not be reading right but it appears to me that you head and tail are not on the same plane... Move the tailstock so that the center point touches the headstock center, the should be EXACT. If not then enguageing them would cause one or the other to flex. If the bearings or bushings in the head are worn it would have room to flex. Tail stock lower than head would push up , and the opposite is true. Higher pushes down.

Is this a new occurance or an on going situation. On going may be a result of manufacturer's error. New may be as simple as cleaning the ways and bottom of the tailstock. Check with any moveable part to see if all is back in place. Flith and collected crud can missplace a series of parts. The centers are in Morris Tapers (?) if so then they may have been inserted askew due to a piece of crude or chip, remove clean and reseat and retest the alignment. (Both Tail & Head)

Hope I understand what you are discribing. but it may be a simple clean and reset or it may be worn bearings and factory miss-alignment from the get-go that created a wear on the bearings and now it is showing up.

[Skew ChiDAMN!!]

Hickory, the MC-900's and MC-1100's are "entry level" swivel-head lathes. It's usuallya simple matter to tweak thngs so the centres line up, but when there's a piece clamped between centres and t/stock pressure applied, the headstock swivel can "flex" a bit like a hinge which effectively throws everything out of whack again.

The trick is to work out exactly why it flexes (usually lack of "clean up" machining after casting) and fixing it economically. Usually a simple matter, just one that most people don't expect.

[Tornatus]

The centers are in Morris Tapers

G'day Hickory

Forgive me, but I just can't help it - I'm an ex-English teacher and serial pedant, so I'm driven to observe that the devices you mention in your helpful advice are Morse Tapers. Presumably they are named after the inventor, but I have no idea if he was related to Samuel ...

The reason the error caught my eye is that I have a particular aversion to a form of English folk-dancing called "Morris Dancing", which involves a bunch of lunatics dressed in weird costumes with lots of bells and dangly things, armed with large thick sticks, leaping about and trying to belt the living daylights out of each other. They appear every year at our National Folk Festival, and greatly frighten children and old ladies, so I'm trying to stamp out any mention of things Morris!

[Hickory]

School Master Tornatus;

Pardon my ignorance, I are knot a great speller... I kin read readin' but I can't write writin'....:o

Perhaps I will slither down in imbarrasment and call them M-T from now on.

Morse was the code guy and Morris was the chair guy, which was the tapered hole guy? :confused:

Skew;

Although I am unknowledgeable of the brand and numbering of this discussed lathe, the same holds true universally. With the introduction of a swival head you have added one more variable to the equasion. Look for crud and curruption or worn componants in yet one more place. Still the point to point alignment stands true and the effect of miss-alignment are the same. In this case it may not be the bearings that are giving away but yet another componant.

[hughie]

. On going may be a result of manufacturer's error.


Some body else on this forum contacted Hare & Forbes, one of the major suppliers of this variety of lathe and their comment was:


"none of the headstocks/tailstocks line up on these lathes"

So its more a case of made to a price to maximize profit and to hell with quality. As Skew says they are entry level lathes.......! only just maybe;)

:D But if your handy most of the problems can be over come. So the next guy that gets my lathe will get one that actually works and works well, :D not to worry. I am gonna put it down to experience and move on.

hughie

[Tiger]

Dear all but particularly TTIT and Skew,

I tried your suggestions regarding filing the cast claws on the headstock bolt and after several attempts and a few hours it's no better than before. The headstock still lifts up. I'm obviously doing something wrong, could you give me more details please so that I can fix this frustrating problem once and for all. I have noticed that when you test the bolt and claws without the headstock that the grip seems ok (don't know if that helps the situation though).

Would really appreciate any help on this one if you've been able to get this to work.

[Gil Jones]

Morse Taper was invented by Stephen A. Morse (also the inventor of the twist drill) circa 1864. Morse Tapers come in eight sizes identified by number between 0 and 7. Often this is abbreviated as MT followed by a digit, for example a Morse taper number 4 would be MT4. The MT2 taper is the size most often found in drill presses up to 1/2" capacity.

[bsrlee]

Hi Tiger. I'll buy in at this point.

Keep the file/s out - the headstock should be touching all around on the bed of the lathe, and until it does rest flat all round without tightening up the bolts, it will keep tilting. You probably need some bearing blue to find out where it is touching - you can use a marking pen but it will stuff the pen in short order, or spray on a thin coat of paint, then rotate the head a few times, take it off & file the bits where the bare metal is exposed - repeat a few times until the gap/s disappear when not tightened down.

Then you 'only' have to worry about what will happen when you tighten the wood up using the tail stock - this will likely involve more grease under the fingernails, cuts & scrathes as you re-adjust the position of the claws on the drawbolts.

If/when all that does not entirely cure the problem, then you may have to file a very slight taper on the base of the headstock so it is prepositioned down by the amount that it rises when pressure is applied. You may also want to look at how tight you are doing up the tailstock against the wood, and possibly get a 'Steb-centre' or something similar to hold the wood in place & just don't screw things up so hard.

[Skew ChiDAMN!!]

If you remove the "bolt & claws," how much lateral movement is there between the headstock and the bed? ie. Can you move it backwards and forwards or side to side by more than a few mm?

It's really not a good swivel/mount system, is it? :( IMHO they would've done better to have the clamping bolt run parallel with the drive spur instead of perpendicular to it. But I guess there's probably some reason they went the way they did. [shrug]

[joe greiner]

bsrlee said "...file the bits where the bare metal is exposed... "

Other way around. In "blueprinting" (has nothing to do with construction plans, BTW), you coat the master surface (in this case the lathe bed) with a thin coat of bearing blue, paint, crayon, marking pen, etc. (Doesn't have to be blue actually). Sacrificial marking pen works well because it makes a very thin coat. Rub/rotate the headstock on the bed as described by bsrlee. File away the marks "printed" onto the workpiece (i.e. the headstock) by the master surface (the lathe bed). Repeat as needed until you get a uniform printed pattern.

This may not correct the immediate problem, however, if the base of the headstock was originally milled non-parallel with the spindle axis. In that case, need to introduce a slight taper by over-filing at the offending location, and repeat the blueprinting process.

In any event, do not consider lapping the two surfaces to each other, because that also affects the master surface.

JG

[RETIRED]

bsrlee said "...file the bits where the bare metal is exposed... "

Other way around. In "blueprinting" (has nothing to do with construction plans, BTW), you coat the master surface (in this case the lathe bed) with a thin coat of bearing blue, paint, crayon, marking pen, etc. (Doesn't have to be blue actually). Sacrificial marking pen works well because it makes a very thin coat. Rub/rotate the headstock on the bed as described by bsrlee. File away the marks "printed" onto the workpiece (i.e. the headstock) by the master surface (the lathe bed). Repeat as needed until you get a uniform printed pattern.

This may not correct the immediate problem, however, if the base of the headstock was originally milled non-parallel with the spindle axis. In that case, need to introduce a slight taper by over-filing at the offending location, and repeat the blueprinting process.

In any event, do not consider lapping the two surfaces to each other, because that also affects the master surface.

JGThis is assuming that the "master surface" is flat, true and paralell to the ways of the bed.

This surface should be checked with a good straight edge first: along, across, diagonally and a few points in between.

[TTIT]

Dear all but particularly TTIT and Skew,

I tried your suggestions regarding filing the cast claws on the headstock bolt and after several attempts and a few hours it's no better than before. The headstock still lifts up. I'm obviously doing something wrong, could you give me more details please so that I can fix this frustrating problem once and for all. I have noticed that when you test the bolt and claws without the headstock that the grip seems ok (don't know if that helps the situation though).

Would really appreciate any help on this one if you've been able to get this to work.Did a bit of a sketch to explain what I found was stopping my MC900 headstock from clamping up properly. Don't know if yours is the same deal but filing the toggle so that it seated squarely before the rod started bending sorted mine out nicely. Basically, both ends of the toggle need to seat at the same time, before any pressure is applied.

[Tiger]

Thanks so far for the replies. I have tried the bearing blue and filed down areas but still not much improvement:mad: . Am I missing something from the TTIT post as it sounded like a simple fix? I'm wondering whether anyone (besides TTIT) has been able to fix this problem without resorting to tapping a bolt through the headstock.

Skew, agreed the bolt should run in line with the drive centre. On my lathe, it only lifts up where the drive centre is.

Was down at Hare and Forbes on Saturday and experimented with their display lathe, could not budge it the headstock and there was no flex, it was easy to swivel and locked with a minimum of turns of the handle. Why can't they make all lathes that way:confused: ?

[Tiger]

Thanks for the sketch, TTIT, I did have it right but I'm still getting that damn flex. Maybe a little more filing but at this rate there'll be no more claw ( .

[Gra]

G'day Hickory
so I'm trying to stamp out any mention of things Morris!

As long as you have no aversion to Morris Garages.:D

[Skew ChiDAMN!!]

Curiouser and curiouser.

Just as a check, I think I'd try getting myself a small pane of float-glass (so you know it's dead-flat) run a very small bead of oil around the top of the mounting ring, in the centre of the face, and lay the glass on top.

By looking at how the oil spreads out, you should see exactly where any dips, bows or mis-machining in the ring is, if any. I doubt it'd be anything this basic, but...

[bsrlee]

Looking at TITT's sketch - OMG!!!!:eek: :eek: :eek:

What a poxy way of holding the headstock down! I'm glad I bought a slightly different lathe from Timbecon - it has an eccentric cam that pulls up on a bolt mounted between the ways and a large shaped piece that rides under the bed - much easier to fit up and less potential for flex/stretch.

Multiple inclined planes and a bolt - you'd have to be King Kong to get that tight enough ever time IMNSHO.

[Tiger]

Looking at TITT's sketch - OMG!!!!:eek: :eek: :eek:

What a poxy way of holding the headstock down!

You've got that right but a lot of the MC900 and equivalents have the same action, now the challenge is to work with what we've go and somehow improve it.

By the way it's not TITT but TTIT, but what's a tit between friends:D

[hughie]

What a poxy way of holding the headstock down! I'm glad I bought a slightly different lathe from Timbecon - it has an eccentric cam that pulls up on a bolt mounted between the ways and a large shaped piece that rides under the bed - much easier to fit up and less potential for flex/stretch.


I agree, my 1100 has a more conventional method of pulling up the plate from underneath against the bed. Much the same as brslees set up. The incline locking set up is a hard way to get it tight, dunno if you will ever succeed....:mad: its just a poor method from the beginning to end..
I wonder what Einstein came up with this idea. :confused: All you can do is improve the fit of the two angled areas so they match each other. Maybe add a backing plate to the clamps to prevent any bending across the clamping rod holes. I suppose its cast iron, so in time it will fail due the excesssive pressure required to hold it from moving. Not good!

[Skew ChiDAMN!!]

Another thought... again a very basic one... is the swivel ring the old style, ie. a part of the bed-casting, or is it of the newer bolt-on type?

If the latter, it is bolted/screwed to the headstock tightly, yes?

(I know, I know... just eliminating the obvious. They're the ones I often miss. :o )

[Tiger]

Skew it it bolted on, from memory there are 3 allen bolts that hold the base down, I'll be doing more analysis and swearing this weekend when I have another look at it:mad: .